In conclusion, I would like to present you with a variant of N-tier architecture: N-tier multi-regions. This variant is designed for high availability and as a disaster recovery infrastructure. Let's take a look at the following diagram:

What is different here? The architecture shown here is divided into three resource groups. Two resource groups (located in two Azure regions) are based on the already presented N-tier architecture and are thus identical. One of these resource groups is called the primary resource group and is for daily use. The other resource group (called the secondary resource group) serves as a failover.

The third resource group only includes an instance of the Azure Traffic Manager as a resource. The Azure Traffic Manager is the new entry point for this architecture and routes incoming requests to one of the regions. During normal operations, it routes requests to the primary resource group. If that region becomes unavailable, the traffic manager fails over to the secondary resource group.

There is another difference in the primary resource group and the secondary resource group —an additional subnet was added, which includes a VPN gateway. With the VPN gateway, you can configure a VNet-to-VNet connection, to enable network traffic between the two VNets.